To facilitate the healing process, modern medical/surgical procedures which include certain orthopedic, plastic, and podiatric operations, often utilize pins and/or screws to positionally fix (or maintain) bones that are broken or fractured. The repair of serious fractures involves arranging and temporarily fixating the fragmented pieces of bone, drilling a hole completely or partially through the broken bones, and inserting a pin or screw into the drilled holes to secure the pieces together. The pins, screws, and/or any fasteners must be of precise length in order to hold the fragments of bone together in a proper state of fixation. If the length is too short, the reduction of the fracture is weak or unstable. Conversely, if the length is too long, the fastener protrudes from the bone into the surrounding tissue, and can damage vital anatomic structures, such as arteries, veins and/or nerves. The depth of drilled holes varies because each bone in the body is unique in shape, size, and thickness. Consequently, surgeons find it necessary and imperative to precisely measure the depth of the completely drilled holes (through holes) or partially drilled holes (blind holes), so that a fastener of correct length can be selected to complete the surgical repair.
The conventional instruments that surgeons use to measure the depth of holes drilled into bone include mechanical gauges that employ various hooks and/or expanding physical elements on one end of a calibrated rod. Mechanical depth gauges typically comprise a central probe member having a barb at the distal (far) end, and a reciprocating sleeve that encircles the proximal (near) end of the central probe member. Conventionally, the central probe member is slidably connected to the reciprocating sleeve, such that central probe member slides freely back and forth to facilitate manual operation and measurement. To measure the depth of a hole in a bone, the surgeon abuts the sleeve against the proximal side of the hole, and manually extends the probe member into the hole. After extending the probe member beyond the distal side of the hole, the surgeon retracts the probe member, attempting to find purchase against the distal side of the hole with the barb. Typically, a marker is secured to the central probe member, and the reciprocating sleeve has a graduated linear scale or display unit along a portion of its length that is read visually (e.g., a mechanical ruler) or electronically (e.g., a linear encoder). The surgeon reads the measurement of depth by examining the position along the graduated scale indicated by the marker, or by reading a display unit attached to the reciprocating sleeve.
Improvements in the conventional analog depth gauge provide for more readable displays (e.g., LCD displays and HOLD buttons, as disclosed in U.S. Pat. No. 7,730,629), and probe tips that include electronic sensors such as optical transducers, inductive loops, etc. (e.g., see U.S. Pat. No. 7,493,703 and U.S. Pat. No. 7,676,943). But even with these improvements, fundamental difficulties persist. Measurement of depth using a conventional depth gauge typically requires significant interaction and difficulty on the part of the surgeon to: 1) manually manipulate a calibrated rod and/or a reciprocating sleeve that encircles a central probe member; 2) precisely locate a bone edge using a barbed hook or time-varying electronic signal from an electronic sensor in the probe tip; and/or 3) make a close examination of a graduated scale. In surgical procedures that require many depth measurements, these difficulties are multiplied.
Conventional methods for measuring the depth/length of a hole that is completely or partially drilled into bone involve tedious mechanical measurements which are made by manual means, and therefore, are subject to potential inaccuracies as a result of human and other errors. There are many complications and costs associated with measurement inaccuracies and placement of incorrect fixation devices into the hole of a bone. Failure to accurately measure the hole in a bone can lead to: 1) a dramatic increase in operating time; 2) increased radiation (X-ray) exposure to the surgeon and/or patient; and/or 3) increased operating costs to the patient and hospital (e.g., due to extended use of facilities, wasting of expensive medical/surgical hardware, higher billable/overtime hours for hospital staff, etc.).